Slides in the southern Whitefish Range

Location Name: 
Forecaster Observation - southern Whitefish Range
Observation date: 
Monday, November 28, 2022 - 15:45
Is this an Avalanche Observation: 
Yes
Observation made by: Forecaster

Tabs

Quick Observation

FAC staff visited the southern Whitefish Range to assess near surface instabilities and snowpack structure.

  • We found 7-8 inches of new snow above 6000 feet. Most of this fell Sunday and was accompanied by several hours of moderate southwest winds with strong gusts.
  • Despite Sunday's breezy conditions, the snow surface remained soft and generally lacked cohesion in most locations. 
  • Shooting cracks and collapsing were common on an open east aspect at 6200 feet. We were able to intentionally trigger narrow soft slabs in the new snow. Slides failed on a layer of weak facets 8-12 inches below the surface. Due to the soft surface slab, slides only propagated 10-15 feet wide.
  • We looked at a rider-triggered slide on a north aspect at 6500 feet. This avalanche failed on the same layer of weak facets about a foot below the surface. Propagation was limited by the soft surface slab to 25 feet or so.
  • The snowpack structure in this area is poor and will probably prove problematic once a sufficient load arrives. Besides the facet layer, most of the pack consists of weak snow. Removing boots from skis resulted in sinking crotch deep and humorous wallowing. 
  • Riding was generally quite fun in all aspects.

 

Snowpack, Avalanche, Weather Images: 
Snowpack, Avalanche, Weather Videos: 

November in Southern Whitefish

Travel Details
Region: 
Whitefish Range - Southern (south of Coal Creek)
Activity: 
Skiing
Snowpack Details
Snowpack and Weather Details: 
Hide Terrain
Elevation of observation: 
5000-6500 ft
Aspect(s) of observation: 
N
NE
E
SE
Red Flags: 
Avalanches from the past 2 days
Shooting cracks
Collapsing / whumpfing noises
Blowing snow
Persistent Weak Layers: 
Surface Hoar
Facets or Faceted Crust
On the surface
Buried
New Snow in the past 24 hours: 
8.00in.
Total Snow Depth: 
50
More comments about the snowpack and weather: 
A cold day with single digits for the high. Northerly winds were lightly drifting snow. Sunny skies gave way to mostly cloudy conditions. The snowpack showed good stability today due to the lack of a surface slab. However, the snowpack structure is weak throughout. We dug two snowpits - one on a south aspect and one near an accidentally triggered slide from Sunday on a north aspect. Ho-hum results in stability tests today, but worrisome weak snow may be a problem when we return to a storm cycle. Please see the snowpit profiles located in the image section of the quick observation tab.
Blowing Snow: 
Light
Wind Speed: 
Light (Twigs in motion)
Wind Direction: 
Northeast
Air temperature: 
Below Freezing
Snow line: 
0
Sky Cover: 
Partly Cloudy (SCT)
Avalanche Details
Avalanche Details: 
Date and Time of Avalanche: 
Monday, November 28, 2022 - 15:00
Number of avalanches: 
2
Avalanche Type: 
Soft Slab
Failure Plane/Weak Layer: 
New/old snow interface
More information or comments about the avalanche: 

Intentionally triggered slides on the layer of facets one foot below the surface. 

Hide Trigger
Trigger: 
skier
Trigger Modifier: 
Intentionally Triggered
Hide Terrain
Start Zone Slope Angle: 
36
Aspect: 
East
Starting Elevation: 
6400
Hide Size
Destructive Size: 
D1.5
Relative Size: 
R1 Very Small
Crown Height: 
1 ft
Avalanche Length (Vertical Run): 
125ft.
Avalanche Width (Average width): 
15ft.
Avalanche Location: